This project is in support of the NTP[unreadable]s High Throughput Screening Program goals which call for the use of novel in vitro approaches to characterize patterns of toxicity for environmentally important chemicals and to develop toxicity signatures for these chemicals for use in triaging chemicals for detailed follow-up testing and ultimately, for predicting in vivo toxicity. One of the toxicity disciplines for which NTP has sought testing applications is Immunotoxicity. To this end, twenty-five model compounds, selected because of interest by NTP scientists in their potential for immunotoxicity, will be tested on 5 lympho-hematopoietic cell populations (a mixture of lympho-hematopoietic stem, progenitor, and precursor cells) from 3 species (human, rat, and mouse) at 6 doses per compound using 6 replicates per dose. The study will be performed using the HALO[unreadable] - 384 HT Platform, developed and validated by Hemogenix, Inc. Cells from the 3 species of interest will be procured by Hemogenix, Inc., and processed for use in this immunotoxicity screening project. The 25 compounds to be tested for immunotoxicity will be provided by NTP and formulated according to requirements specified by Hemogenix (stock concentration, vehicle, coding information, etc). Hemogenix, Inc., will make the appropriate serial dosing dilutions from the stock solutions provided by NTP. Human cells will be incubated for 5 days with test compounds;rat and mouse cells will be incubated for 4 days. Hemogenix, Inc., will collect the resulting data and prepare a final project report detailing the results of the study.